In Japanese Laid-Open Patent Publication No. 09-248678, an X-type spot welding gun is disclosed, which opens and closes a movable side gun arm by a servo motor through a speed reducing device and a crank mechanism, and controls an output torque of the servo motor such that a pressing force applied during welding becomes constant, corresponding to a crank angle at a time that pressure is applied.
In Japanese Laid-Open Patent Publication No. 2001-198680, a structure is disclosed in which, in a resistance welding machine (welding gun) having an electrode tip operated by an air cylinder, the electrode tip is attached to the air cylinder through a holder. In the case of this structure, linear displacement of a piston rod of the air cylinder directly displaces the electrode tip without modification in a linear manner.
In Japanese Laid-Open Patent Publication No. 2004-351476, an air pressurization type welding device (welding gun) is disclosed in which a moving electrode is attached to an air cylinder through a shank. In the case of this structure as well, linear displacement of a piston rod of the air cylinder directly displaces the moving electrode without modification in a linear manner.